66 GRAMINEAB (GRASS FAMILY) 



much shorter than the pedicels: glumes l-nerved, acute, half shorter than the 

 spikelet; lemma keeled, 3-nerved (lateral nerves prominent), scabrous- 

 pubescent, erose denticulate at apex, mucronate, villous at base. Graphe- 

 phorwm flexitosum. — Plains of Colorado and adjacent regions. 



47. DIPLACHNE Beauv. 



Perennial grasses with abundant narrow leaves. Spikelets 2-12-flowered, 

 linear, compressed or subterete, sessile or short-pediceled, on the lower sides of 

 the rays of the racemose panicle (rarely in a simple spicate panicle) : rays hori- 

 zontal to nearly erect, spikelet-bearing to the base. Glvunes l-nerved, acute or 

 somewhat tridentate, the second larger but not exceeding the adjacent floret; 

 lemma membranaceous, rarely rigid, obtuse, truncate or acute, sometimes 

 short-awned or 3-toothed, often pubescent on the 3 nerves near the base, 

 slightly exceeding the palet. Grain translucent, amber-colored, oblong, or 

 subterete. Intemodes of rachilla glabrous. 



1. Diplachne acuminata Nash, Brit. Man. 128. 1901. Culms tufted, 3-6 

 dm. high, simple or branching: leaves very rough, usually involute when dry: 

 racemes numerous, ascending: lemma 6-7 mm. long, entire and acuminate or 

 sometimes obscurely 2-toothed, the midnerve extending into an awn. D. 

 fascicidaris. — Colorado to Nebraska and south to Arkansas. 



48. ERAGROSTIS Beauv. 



Perennials or annuals, usually with numerous leaves somewhat pilose at the 

 ligule. Spikelets 3-30-flowered, compressed, awnless, perfect except the upper 

 floret. Panicle usually large and spreading, rarely contracted or subcapitate; 

 rachilla usually persistent with the palets. Glumes ovate, acute, or subob- 

 tuse, smooth or sUghtly hispid on the keel; palets arched, 2-keeled, slightly 

 shorter than the lemma. Grain oblong or globose, semitranslucent, amber- 

 colored, terete or with a shallow channel. 



Spikelets 2-3 mm. wide . . 1. E. major, 



Spikelets 1-2 mm. wide 2. E. piloss. 



1. Eragrostis major Host. Gram. 4: t. 14. 1809. Culms 2-5 dm. high, 

 leafy: leaves flat, 4-8 mm. wide: panicles rather densely flowered, oblong, 

 1-2 dm. long: spikelets sessile or short-pediceled, 6-15 mm. long, 6-20-flowered: 

 upper glume somewhat 3-nerved; lemma obtuse, prominently nerved, one- 

 fourth longer than the ciUate palet: grain subglobose, 0.8 mm. in diameter.-.^' 

 Introduced everywhere in the United States and northern Mexico. 



2. Eragrostis pilosa (L.) Beauv. Agrost. 71. 1812. Culms 2-5 dm. high, 

 rather weak: leaves usually pilose at the ligule: panicle 1-2 dm. long, diffuse; 

 branches 5 cm. long or less: spikelets 3-6 mm. long, 4-8-flowered; florets 

 rather loose on the elongated rachilla: glumes unequal, about one half as long 

 as the contiguous florets; lemma nearly smooth, subacute, sUghtly exceeding 

 the smooth palet: grain oblong, smooth, nearly 1 mm. long. — The native form, 

 which has been called E. Purshii, does not seem to be distinct from the in- 

 troduced species here described; one or both of the forms occur in most por- 

 tions of the United States. 



49. EATONIA Raf. 



Erect grasses with slender simple culms and usually flat puberulent leaves. 

 Spikelets usually 2-flowered, with a naked pedicel-like rudiment, compressed, 

 cuneate, awnless, perfect, numerous, short-pediceled or nearly sessile on the 

 verticillate branches of the rather slender panicles; rachilla smooth, articu- 

 lated above the thin herbaceous glumes. First glume narrowly lanceolate, 

 l-nerved; second glume broad, obovate, 3-nerved; lemma lance-oblong, her- ' 



